In the case of a general axial flow fan, air flow which flows out from the blowout opening tends to diffuse to the outer periphery direction, and the static pressure is not raised. Japanese Laid-open Patent Application Publication No. 2008-261280 reports an example which gives a devised stationary blade, in order to overcome this problem. From this, in the configuration of Japanese Laid-open Patent Application Publication No. 2008-261280, there is a possibility that a higher static pressure efficiency (=(static pressure×air flow quantity)/power consumption) is obtained, as compared to the static pressure efficiency of a conventional axial flow fan.
In Japanese Laid-open Patent Application Publication No. 2008-261280, a stationary blade is disclosed which is divided to two parts of an inner side and an outer side by an annular ring. The blade width of the outer side stationary blade is made larger than the blade width of the inner side stationary blade. Therefore, in the region away from the central axis, a component turning in the circumferential direction of the air flow through the outer stationary blade is converted to the central axis direction efficiently, and in the region close to the center axis, the influence of the resistance which the air flow receives can be reduced. As a result, the static pressure-air flow quantity characteristics can be improved, they say.
However, with regard to the configuration of the stationary blade disclosed in Japanese Laid-open Patent Application Publication No. 2008-261280, many items to be designed exist, such as how to set the far extent of the inner side stationary blade from the central axis and from where the outer side stationary blade is to be defined, and how to design the shape of each of the two stationary blades of the inner side stationary blade and the outer side stationary blade, and so the cost for designing increases. Further, because the structure of the stationary blade including the annular ring structure is complicated, the metal mold grows expensive. Thus, with the complicated structure of the stationary blade, the manufacturing cost increases and as a result, a rise in the product price is caused.